#yuki939

a,b=map(int,raw_input().split())
k=1
x=0
for i in range(32):
 if k&a>0:
  if k&b==0:
   x-=1
   break
 else:
  if k&b>0:
   x+=1
 k<<=1
if x==-1:
 print 0
elif x==0:
 print 1
else:
 print 2**(x-1)